Which is an example of a couplet from Shakespeare’s “Sonnet 18”?

Shakespeare's "Sonnet 18" is one of his most famous and beloved poems, and it is notable for its use of a specific poetic form known as the sonnet. A sonnet is a 14-line poem written in iambic pentameter, with a specific rhyme scheme. The last two lines of a sonnet often comprise a couplet, which is a pair of lines that rhyme with each other and provide a kind of summary or conclusion to the preceding lines.

The couplet in "Sonnet 18" reads:
So long as men can breathe or eyes can see,
So long lives this, and this gives life to thee.

This couplet serves as a kind of resolution to the rest of the poem, which has been dedicated to describing the beauty and perfection of the poem's subject. The couplet asserts that the beauty and perfection of the subject will never fade, as long as there are people who are able to appreciate it. In this way, the couplet reinforces the idea that the subject of the poem is truly eternal and immortal.

This particular couplet is also interesting in that it uses the word "this" twice, which refers to the poem itself. The couplet suggests that the poem itself is what gives the subject of the poem eternal life, which is a fascinating metapoetic conceit. This idea that poetry can transcend its own time and give eternal life to its subjects is a theme that runs throughout many of Shakespeare's sonnets, and it is one of the reasons why they continue to be so beloved and enduring to this day.